Panel substrates used for conventional liquid crystal display panels have been exclusively made of inorganic glass, and plastic panels have not yet been put to practical use. While there are a number of reasons for that, it is, basically, because there are problems involved with orientation treatment in addition to many problems with properties of plastics, sealing agents and sealing methods. These various problems are now being ameliorated one by one, and this invention is based on the success in establishing a unique orientation treatment technique applicable especially to plastic panels, as the result of our study on, among these various problems, how orientation treatment of plastic panels should be effected instead of an attempt to apply the techniques which have been employed for orientation treatment of inorganic glass panels to plastic panels.
Orientation treatment means employed for inorganic glass panels may be classified into:
(a) a method by angular deposition; PA1 (b) a method by radiation of accelerated ions; PA1 (c) a method by rubbing; PA1 (d) a method by bonding an elongated film; PA1 (1) a saturated polyester; PA1 (2) a reaction product of a saturated polyester and a reinforcing additive; PA1 (3) a mixture of a saturated polyester and nylon; PA1 (4) a reaction product of a saturated polyester, nylon and a reinforcing additive; PA1 (5) a reaction product of a low melting point copolymerized nylon and a reinforcing additive.
and so forth. More particularly, the method by rubbing is further classified into a method by rubbing after coating an organic silane compound, a method by rubbing after coating a heat-resistant polymer material, and the like.
However, none of these methods is effective on plastic panels. That is, the method (a), in which SiO.sub.2 is deposited on a glass substrate at an angle of up to 65.degree., requires that the substrate be heated to 200.degree.-300.degree. C., which temperature is more than that plastic films can withstand. Further, the method (b), in which accelerated ions are radiated from a shower-like ion generator onto a substrate leaning at an angle of up to 65.degree., not only requires expensive equipments and complicated operation but also cannot achieve mass-productivity and therefore it is unsuitable as orientation means for plastic panels which originally aims mass production and hence reduction in cost.
Further, with the rubbing method (c), organic silanes are poor in adhesion with plastics and in orientation properties, heat-resistant polymer materials which form films having good orientation on glass substrates cannot be adopted because a temperature of 300.degree. C. or higher is employed for film forming, and films of other polymer materials known for glass substrates do not show good orientation properties on plastic panels.
Furthermore, with the method (d), which is to bond an extremely thin monoaxially elongated film, it is quite difficult to bond this extremely thin film on a plastic film without remarkably reducing the resistance value of a conductive film. In either case, any known orientation treatment means for glass substrates is not suitable for plastic panels.
For orientation treatment of plastic panels, various conditions different from those for glass panels are required.
The first requisite is that physically and chemically stable horizontal orientation performance be achieved at a temperature below the maximum temperature up to which a plastic film can withstand, the second requisite is that continuous production be enabled and large-scale equipments or complicated operation be eliminated, and so forth.
It is an object of this invention to provide liquid crystal display panels inexpensively by mass production using orientation treated films, and a process for their production. It is another object of this invention to provide liquid crystal display panels having constantly high quality although by inexpensive mass production. Other objects of this invention are believed to be easily understood from the following description and therefore not mentioned herein.